Organic peroxides such as, for example, dibenzoyl peroxide are useful as, among others, initiators in polymerization processes. Because of the flammable and explosive nature as well as high shock-sensitivity of organic peroxides, organic peroxides generally are diluted with inert substances such as, for example, plasticizers. See Kirk-Othmer Encyclopedia of Chemical Technology, Third Edition, Vol. 18, pages 111-183 (1982). Also because of the dangerous properties of the organic peroxides, the United States Department of Transportation requires yellow organic peroxide labels for organic peroxide compositions having greater than 35 weight % of organic peroxide levels. A phlegmatization process to reduce the organic peroxide levels in the compositions to lower than 35% so that no yellow labels are required for shipping and storage is very desirable.
However, attempts to reduce the organic peroxide levels to below 35% by increasing a plasticizer such as, for example, dicyclohexyl phthalate were unsuccessful because the resulting compositions were found to yield parts with splotchy areas and brittleness. In others words, an organic peroxide composition which does not require yellow labels cannot be produced by increasing the concentration of the plasticizer.
Organic peroxide compositions are also commercially available in paste forms containing butyl benzyl phthalate or dibutyl phthalate as plasticizer. These paste forms have a tendency to separate into phases and are difficult to accurately measure. Dibenzoyl peroxide is commonly available as a wetted granular material in which the water acts to reduce the shock-sensitivity. However, for some polymerization processes such as, for instance, the curing of polymers, the presence of water in the peroxide is often unacceptable because water can often react with the polymers in the polymerization process causing undesirable results.
It would therefore be a significant contribution to the art if an organic peroxide composition that is substantially water-free, non-dusting, flowable, and safe during storage, shipping and handling (i.e., does not require yellow labels), can be developed.